Bicycle Drivetrain Toggle Mechanism for Variable Torque Transfer
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Solution Overview
Problem
Existing drivetrains for bicycles transmit a substantially constant torque throughout the pedal rotation cycle, failing to adapt to the variable power generated by a cyclist's muscles, and suffer from issues like chain retention and engagement with oval chainrings.
Innovation Solution
A drivetrain with a toggle mechanism that converts pedal crank rotation into a reciprocating rectilinear motion, using an eccentric circular guide and toggle mechanism to transfer variable torque to the wheel, optimizing torque transmission during the pedaling cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant torque transmission system is used, then the drivetrain structure is simple, but the power transfer efficiency is reduced because it cannot adapt to variable muscle power generation
Solution Approach 1:
The patent applies the dynamics principle by making the torque transmission variable rather than constant. The toggle mechanism dynamically adjusts the transmission ratio based on the pedaling phase, allowing the drivetrain to adapt to the variable power generation characteristics of human muscles during different portions of the pedal stroke cycle.
Solution Approach 2:
The patent changes the transmission ratio parameter dynamically through the toggle mechanism. By varying the geometric configuration of the toggle links during pedaling, the system modifies the torque multiplication factor to match the instantaneous power output of the cyclist, thereby optimizing power transfer efficiency across different pedaling phases.
2Productivity
If oval chainrings are used to match variable power generation, then power output increases slightly, but chain retention and engagement problems occur
Solution Approach 1:
The patent replaces the traditional chain-driven mechanical system with a direct gear engagement system. The toggle mechanism connects the crankset directly to the rear wheel through rigid mechanical links rather than relying on a chain, eliminating chain retention and engagement issues while maintaining the ability to vary torque transmission.
Solution Approach 2:
The patent segments the torque transmission function across multiple rigid links in the toggle mechanism rather than relying on a single chain-driven chainring. This segmentation allows each component to be optimized for its specific function while maintaining reliable mechanical connection throughout the power transmission path.
3Productivity
If oval chainrings are used to improve power transfer, then there is modest power gain, but the system becomes difficult to couple with derailleur for gear shifting
Solution Approach 1:
The patent uses the dynamics principle to create a variable transmission ratio system through the toggle mechanism's changing geometry during pedaling. This dynamic adjustment replaces the need for complex derailleur systems while achieving similar or superior power transfer efficiency across different resistance conditions.
Solution Approach 2:
The toggle mechanism serves multiple functions simultaneously: it varies the transmission ratio to match muscle power output, provides direct drive connection eliminating chain issues, and works with both single-speed and multi-speed configurations. This multi-functionality reduces overall system complexity compared to combining oval chainrings with derailleur systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The drivetrain effectively multiplies force applied during weaker muscular phases, providing uniform torque to the wheel throughout the pedaling cycle, improving power transfer and reducing maintenance needs.
Implementation Method 1
The support comprises a circular guide, the geometric centre of which is arranged eccentric with respect to the rotation axis of the central axle
Implementation Method 2
the drivetrain further comprises a toggle mechanism connecting the support to the wheel of the vehicle
Data Source
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AI summary
The present invention relates to a drivetrain (10) for vehicles comprising at least one drive wheel, the vehicle including at least one support (20, 30) rotating integrally with a central axle (11) and with the pedal cranks (15, 16), and a toggle mechanism (40, 50) connecting the support (20, 30) to the wheel (130), wherein the toggle mechanism (40, 50) is connected to a slide (45, 55) that is slidable with respect to the frame (110), and wherein a rotary movement imparted to the pedal cranks (15, 16) is transformed into a reciprocating rectilinear motion of the slide (45, 55), the drivetrain further comprising a gear (48, 58, 49, 59) that connects the slide (45, 55) to the wheel (130) of the vehicle to transform the reciprocating rectilinear motion of said slide into a rotary motion of the gear to provide, in an active phase, a torque to the wheel (130).